Transformation of expanded polymers

ABSTRACT

The invention concerns the transformation of expanded polymers, in particular styrene polymers of the polystyrene type and styrene copolymers. More particularly it concerns a method for transforming polymers in an expanded solid state into a non-expanded amorphous state in the form of a re-usable malleable pasty magma. The method comprises a step for treating the polymer with a transforming solution containing a solvent, a non-fatty lubricant and optionally an alcohol. The invention concerns the transformation method proper, the transforming solution used in said method, the device for implementing said method and the magma resulting from implementing the method.

CROSS REFERENCE TO RELATED APPLICATION

The present application is the national stage under 35 U.S.C. 371 ofPCT/FR98/01715, filed Jul. 31, 1998.

The present invention relates to a process for the conversion ofpolymers, preferably expanded polymers such as expanded polystyrene.More particularly, the present invention relates to a process for theconversion of polymers from an expanded solid state to a non-expandedamorphous state in the form of a reusable, pliable, pasty intermediatemagma. The invention relates to the conversion process proper, theconversion solution used in said process, the device for carrying outthe process of the invention, and to the magma obtained after carryingout said process, and articles produced from said magma.

The use of expanded polymers of the polystyrene type is very widespread.This use, although very beneficial in view of the low cost and the greatease of handling of expanded polystyrene (EPS), has resulted in thegeneration of considerable amounts of EPS wastes which are difficult torecycle.

Until now, two solutions have been put forward to enable industries asvaried as the agro-food industry, the construction industry and, moregenerally, the handling industry, to dispose of their EPS wastes: eitherthe destruction or the recycling of EPS.

The destruction of EPS is carried out by incineration at hightemperatures. Apart from the high costs associated with the constructionand operation of the incineration plants, the destruction of EPS givesrise to the dissemination of toxic substances into the atmosphere.

With regard to EPS recycling, the methods currently available generallypropose grinding used packaging made of expanded polystyrene andreintroducing it into the production process. This type of process isattractive but has some major disadvantages.

Amongst others, the cleanness of the EPS packaging to be recycled is avital condition if it is to undergo appropriate recycling. Moreover,recycling EPS implies the grinding and appropriate granulation thereof.These steps make effective EPS recycling very complicated.

The present invention provides firstly, therefore, a process for theconversion of polymers without risk to man and the environment whichenables this type of waste to be upgraded in an effective and profitablemanner.

The process is simple, effective and inexpensive and, unlike the currentrecycling processes, does not necessarily presuppose that the wastes tobe recycled be very clean. The process of the invention makes itpossible to obtain a pasty semi-finished material which can then be usedby all the conventional processes of injection, extrusion or moulding inthe plastics industry. This material may also be used to produce variousarticles, particularly insulation or joining articles. The consistencyof the material obtained once solidified is similar to that of a plasticresin.

The present invention relates, therefore, to a process for theconversion of a polymer, essentially an expanded polymer, characterisedin that:

said polymer is treated with a conversion solution comprising:

a major proportion of a solvent making it possible to modify thephysical state of said polymer from an expanded solid state to anon-expanded amorphous state such as to obtain a pliable, pastyintermediate magma,

a minor proportion of a non-greasy lubricant in a sufficient amount togive said magma a non-sticky surface state and, if necessary,

a minor proportion of an alcohol in a sufficient amount to bind saidsolvent and said lubricant in said solution,

said magma is recovered and, if necessary,

all or part of said solvent is evaporated.

The present invention will now be described in more detail and, for abetter understanding of certain preferred embodiments, it will benecessary to refer to the attached figures in which:

FIG. 1 represents a diagram illustrating the steps of an embodiment ofthe process of the present invention;

FIG. 2a is a schematic representation of an embodiment of a device forconversion by immersion according to the present invention;

FIG. 2b is a schematic representation of an embodiment of a device forconversion by spraying according to the present invention;

FIG. 3a represents a side view of the main elements of the device forconversion according to the invention;

FIG. 3b represents a top view of the device of FIG. 2a;

FIG. 4a represents a top view of a preferred embodiment of a treatmentvessel of the conversion device of the present invention;

FIG. 4b represents a transverse section of a treatment vessel accordingto line AA of FIG. 4a;

FIG. 5a is a schematic representation of a feed system for the untreatedpolymer;

FIG. 5b represents a transverse section of a treatment vessel connectedto a feed system for the untreated polymer;

FIG. 6 represents a diagram illustrating the steps of a preferredembodiment of the process of the present invention;

FIG. 7 represents a preferred device for carrying out the process of theinvention;

FIG. 8 represents a grinder which may be used in the process of theinvention.

The process according to the invention makes it possible to obtain amagma of uniform and homogeneous consistency. The consistency of thematerial obtained once this magma has solidified is similar to a plasticresin.

The magma obtained after treatment of the polymer by the process of theinvention is the result in particular of a change in the expandedpolymer to a polymer having a structure and consistency similar to aconventional pasty resin. It is a pliable, pasty magma containing smallamounts of solvent which allow its pasty consistency to be retaineduntil drying.

Without wishing to be bound to a particular theory, it seems that theconversion of polymers, particularly polymers of the EPS type to apliable, pasty magma is the result of internal pressure effects exertedon the polymer by the conversion solution yet without modifying thechemical bonds between the monomers forming said polymers and, probably,without there being any major interactions with the polymer itself interms of its structure. The conversion solution, during its reactionwith the polymer, makes it possible to obtain a collapse of the internalstructure of the latter by replacing air molecules trapped in itsstructure by small amounts of solvent. The magma thus obtained mayretain its pliable, pasty character over a long period of time,generally more than two years. To this end, it is sufficient that themagma be kept in a small amount of solvent and preferably away from air.

The invention relates in particular to the recycling of expandedpolymers of the EPS type.

Unlike the known processes, it is not absolutely necessary for theexpanded polymer to be recycled to be free from impurities. As describedin more detail below, it will be possible to adjust the operatingparameters of the process according to the type of polymer to beconverted.

It should be noted that although the polymer whose recycling isprimarily envisaged is EPS, other types of polymers, expanded orotherwise, may be converted by carrying out the process of theinvention. Styrene copolymers may be mentioned in this connection.

Although it is preferable to grind the elements of polymer to berecycled before bringing them into contact with the conversion solution,grinding is not absolutely necessary. In fact, the time required for thepolymer treated to collapse will depend rather on the diameter of theparticles, generally beads, forming its structure. The greater thisdiameter, the greater the air content of the polymer and the more rapidits reaction to the treatment and hence the more rapid its collapse.

If particularly clean EPS wastes in a small volume are used, it is notnecessary to grind the polymer to be recycled.

Depending on its origin, it may be useful substantially to remove waterfrom the polymer before bringing it into contact with the conversionsolution. It has been observed, in fact, that the presence of watermight cause a dry product to be obtained instead of a pliable, pastymagma. Water may be removed by any conventional method, for exampleusing a stream of air at ambient temperature or hot air.

The conversion solution used in the process of the invention comprises,as solvent, a compound such as acetone. Such a compound is particularlypreferred within the context of the invention. However, other productssuch as certain higher alcohols, benzene, chloroform or methylenechloride, tetrachloroethylene, carbon tetrachloride, toluene ortrichloroethylene may be envisaged in so far as the basic structure ofthe polymer to be treated is kept intact.

Some of the solvents listed above may prove to be too aggressive for thepolymer in high concentrations. In that case they may lead to adeterioration in the basic structure of the polymer. Tests relating tothe concentration to be used and the type of solvent that may be usedmay be carried out easily by the skilled person.

The proportion of solvent in the conversion solution used for carryingout the process of the invention will generally be very high in relationto the other constituents of the solution. The skilled person may choosethe appropriate proportions but these proportions should preferably bebetween 90% and 99% by volume of the conversion solution. In the case ofacetone which has proved to be the most attractive solvent hitherto, theproportions of this solvent in the conversion solution generally rangefrom 94% to 98% by volume of the conversion solution, with a preferredpercentage around 97%.

The lubricant is the second important constituent of the conversionsolution used in carrying out the process of the invention. Theproportion of lubricant must be chosen such as to obtain a pasty magmahaving a non-sticky surface state and thus giving said magma wettingproperties. In the absence of such a lubricant, a resin having a crazedsurface state once the solvent has evaporated is obtained in most cases.Thus, the lubricant according to the invention makes it possible tocontrol the surface tension during drying, this being responsible forfissures. Moreover, the lubricant generally makes the pasty magma mucheasier to handle.

The type of lubricant which may be used in carrying out the process ofthe present invention may be chosen without difficulty by the skilledperson, in the knowledge, however, that it should preferably be anon-greasy lubricant. Glycerol is a lubricant of choice but othernon-greasy lubricants such as polytetrafluoroethylenes, particularlythose sold under the Teflon® brand, may also be considered.

The proportion of lubricant in the conversion solution of the inventionis relatively small compared with that of the solvent. The proportiongenerally ranges from 1% to 10% by volume and preferably from 1% to 3%by volume.

Until now, glycerol has proved to be the most attractive non-greasylubricant. It is generally used in proportions ranging from 1% to 2% byvolume of the conversion solution. In a preferred embodiment of theinvention, the percentage of glycerol is around 1.7%.

The incorporation of an alcohol in a small amount in the conversionsolution of the invention is optional although desirable. The role ofthis alcohol is to bind the two other constituents of the solution inorder to reduce as much as possible the internal phenomena ofdissociation of the magma obtained.

The choice of suitable alcohol may also be made by the skilled person.The alcohol used is preferably an ethyl alcohol 95°, more preferablyethyl alcohol although other linear or branched alcohols having between1 and 15 carbon atoms may also be used.

The proportions of alcohol in the conversion solution of the presentinvention are small. They generally range from 1% to 6% by volume of theconversion solution and preferably from 1% to 2% by volume. In apreferred embodiment of the invention using ethyl alcohol 95°, thepreferred percentage of this alcohol is around 1.3% by volume.

It is important to note here that the concentrations of alcohol andlubricant directly influence the final fluidity of the pasty magmaobtained. In this regard, a reduction in the concentrations of alcoholand lubricant in favour of the solvent increase the fluidity of themagma obtained. For example, a conversion solution containing 96% ofacetone makes it possible to obtain a more solid intermediate magmawhereas a conversion solution containing 96.5% of acetone makes itpossible to obtain a much more fluid magma

The skilled person may thus vary the concentrations of the variousconstituents of the conversion solution depending on the finalconsistency required for the pasty magma.

According to another aspect of the invention, it also relates to theconversion solution described above and to its use for the conversion ofpolymers from an expanded solid state to a non-expanded amorphous statein order to obtain a pliable, pasty magma.

The present invention also relates to a device for the conversion, byway of a conversion solution, of polymers, particularly expanded styrenepolymers of the expanded polystyrene type and styrene copolymers, froman expanded solid state to a non-expanded amorphous state in order toobtain a pliable, pasty magma. Said device is characterised in that itcomprises a treatment vessel capable of receiving the polymer to beconverted, and suitable means of introducing the conversion solutioninto the treatment vessel such as to permit contact between the polymerand the conversion solution in order to confer a non-expanded amorphousstate on the polymer. The device also comprises, if necessary, means ofremoving the magma and means of filtration to permit the removal ofimpurities therefrom.

More particularly, the device is composed of a vessel comprising:

an entry port for the polymer before treatment;

an outlet port for the polymer after treatment; and

a series of nozzles arranged on the internal periphery of the vessel andallowing the conversion solution to be sprayed onto the polymer passingthrough said vessel.

The means of removing the paste are more particularly composed of anendless screw mechanism arranged downstream of the treatment vessel. Themeans of filtration are generally composed of a hopper situateddownstream of the means of removal.

The device of the present invention may also comprise means of storingand grinding the polymer before treatment by the treatment solution.

FIG. 1 illustrates the steps for carrying out the process of the presentinvention. As illustrated by way of example, EPS boxes 10 first undergoa grinding step 20. The granules thus obtained are stored in a suitablesilo 30. The granules are then converted in the conversion device 40either by immersion in a conversion solution or by spraying saidsolution. Said conversion is followed by filtration of the impurities 50and kegging 60 of the amorphous magma thus obtained.

1) Grinding the Polymer

As mentioned above, the step of grinding the polymer prior to its use incarrying out the process of the invention is not absolutely necessary,particularly if the polymer to be recycled contains little or nocontamination by impurities.

However, if the process of the invention involves spraying theconversion solution onto the polymer to be recycled, it is preferable togrind the latter beforehand.

The diameter of the polymer beads and particularly of ground EPS may beadjusted without difficulty by the skilled person such that the sprayingof the conversion solution permits the rapid change from an expandedsolid state to a non-expanded amorphous state of the polymer to betreated.

2) Application of the Conversion Solution

a. Immersion

If the polymer to be recycled is clean or exhibits little contaminationby impurities, it is recommended that the process of the invention becarried out by immersing the polymer to be treated in the conversionsolution. It is preferable not to immerse moist polymer in a bath ofconversion solution because the water contained in the polymer wouldrapidly reduce the conversion capacity of the solution, and the timerequired for it to change from an expanded solid state to a non-expandedamorphous state would increase rapidly after successive treatments.

However, immersion of the polymer of the EPS type in a tank containingthe conversion solution may prove useful if small amounts of polymer areto be converted. In this type of operation, the minimum amount ofconversion solution to be used is 1 l per kilogram of polymer to betreated. The optimum amount of conversion solution to be used rangesfrom 1.5 l to 2 l per kg of polymer to be treated.

b. Spraying

Spraying is preferred because it allows large amounts of polymer to betreated more rapidly using minimal amounts of conversion solution.

Spraying involves spraying the most exact amount possible of solutionwhich is metered as a function of the amount of polymer to be treated,which makes it possible to prevent the accumulation of water orimpurities in the solvent.

The optimum amount of conversion solution to be used may generally beassessed according to the following equations:

M=Q+S

(Q×0.75)+Q=M

where Q is the amount of polymer to be treated (in kg);

S is the conversion solution (in kg); and

M is the amount of magma obtained (in kg).

In other words, one kilo of EPS treated using 0.75 kg of conversionsolution will allow 1.75 kg of pasty magma to be obtained.

3) Filtration of the Magma

The magma obtained is generally filtered so as to remove the majority ofits impurities. Normally, the consistency of the magma obtained is suchthat it is possible to pass it through a hopper without too muchdifficulty. The diameter of said hopper will depend on the amount andnature of the impurities present in the polymer and on the consistencyof the magma obtained. The diameter of the hopper and the averagepressure applied during filtration may be adjusted without difficulty bythe skilled person.

4) Other Parameters

The process of the present invention may be carried out entirely atambient temperature. If the acetone, glycerol and ethyl alcohol form theconstituents of the conversion solution, it is possible to handle thepaste with bare hands without risk. It is also possible to obtain aself-coloured magma, if necessary.

Once the magma has been obtained at ambient temperature, thesolidification time of the articles moulded or extruded from this magmais about 48 h. The magma may, however, be kept in this amorphous statefor a very long period of time by immersing it in a small amount of theconversion solution.

It is, of course, possible to reduce the solidification time of thearticles moulded or extruded from the magma to a few seconds by curingsaid articles. Additional details concerning the conversion of the magmato finished articles will be provided below.

1) Conversion by Immersion

The device for conversion by immersion is illustrated schematically inFIG. 2a. This device, represented in a general manner by referencenumber 100, comprises, in a preferred embodiment thereof, a firststorage tank 110 for EPS connected to a grinder 112, itself connected toa treatment vessel 130. A second storage tank 120 for the conversionsolution is connected to a pump 122 making it possible to feed thetreatment vessel 130. This treatment vessel 130 is also connected to apump 140 connected to a filter 150 and to a storage vessel 160 for themagma.

If the device for conversion by immersion 100 is used, a predeterminedamount of conversion solution is pumped into the treatment vessel 130 byway of pump 122. The EPS is then placed in the treatment vessel 130 suchas to be immersed in the conversion solution. The magma 132 is depositedon the bottom of the treatment vessel 130 and is then pumped by pump 140through the filter 150 to the recovery vessel 160.

2) Conversion by spraying

A schematic representation of a first embodiment of a device forconversion by spraying, illustrated in general manner by referencenumber 200, is shown in FIG. 2b. This device comprises a first storagetank 210 for EPS connected to a grinder 212, itself connected to asecond storage tank 214 connected directly to a treatment vessel 230.The device 200 also comprises a storage tank 220 for the conversionsolution connected to a pump 222. The pump 222 is connected to atreatment vessel 230 and more particularly to a series of atomisers 232arranged on the periphery of the treatment vessel 230. The treatmentvessel 230 is connected to a pump 240, itself connected to a filter 250,connected to a storage tank 260 for the magma.

If the treatment of a polymer of the EPS type is carried out by way ofthe device for conversion by spraying 200, the pump 222 is actuated inorder to form, by way of the atomisers 232, a fine drizzle of theconversion solution inside the treatment vessel 230. The EPS 270 is thendeposited by gravity in the treatment vessel 230. The skilled personwill easily be able to adjust the rate at which the EPS will bedeposited in the treatment vessel 230 as a function of the height ofsaid vessel and the rate of spraying of the conversion solution.

Once the magma 232 has been deposited on the bottom of the treatmentvessel 230, the pump 240 enables it to be passed through filter 250 thento be stored in drums 260 which may be hermetically sealed.

Another embodiment of the device for conversion by spraying isillustrated in FIGS. 3a, 3 b, 4 a and 4 b. With reference now to FIG.3a, the device for conversion by spraying, illustrated in a generalmanner by reference number 300, comprises a treatment vessel 310 theupper part of which comprises an opening 311 allowing the introductionof the EPS to be treated. The treatment vessel 310 is connected in itslower part 314 to means of removal 330 for the magma. These means ofremoval 330 are connected to a filter 340, itself connected to an outletport 350 for the magma. A drum 360 allows the magma to be received aftertreatment.

With reference now to FIG. 3b, the means of removal 330 for the magmaare composed preferably of an endless screw 332 actuated by a motor 334.This endless screw 332 allows the magma to be removed through filter 340to drum 360.

In a preferred manner and as illustrated in FIG. 3b, the treatmentvessel 310 is circular. The treatment vessel 310 and the means ofremoval 330 are preferably produced from smooth pieces making itpossible to prevent as far as possible the magma sticking either to thewall of the treatment vessel 310 or to the endless screw 332 of themeans of removal 330. It is preferable to use stainless steel alloys,particularly alloys of the Inox 304 L type.

The treatment vessel 310 is illustrated in a more detailed manner inFIG. 4a which represents a top view of said vessel. The vessel 310comprises, arranged on the periphery of its internal wall, a series ofspray nozzles 312. Said spray nozzles 312 have a spray angle 313 with asufficiently large range to bring about spraying of the conversionsolution over the entire surface of the vessel 310 such as to obtain anatmosphere highly charged with conversion solution and to allowhomogeneous vaporisation over the EPS falling into the treatment vessel310.

As illustrated in FIG. 4b, the spray angle 317 of the spray nozzles 312is provided such that spraying takes place homogeneously over the entireinterior surface of vessel 310. The spray nozzles are preferablydirected towards the lower part of vessel 310. The aim of this is toprevent the formation of magma on the nozzles 312. The spray angles ofthe spray nozzles 312 are generally about 60° and may be adjusted by theskilled person depending on the volume of the treatment vessel 310.

With reference again to FIG. 3a, if the process of the invention iscarried out using the device for conversion by spraying 300, the EPS tobe converted is placed in the treatment vessel 310 through the opening311 after the nozzles 312 illustrated in FIGS. 4a and 4 b have beenactuated such as to spray the treatment solution over the EPS.

The magma deposited on the bottom of the treatment vessel 310 is removedby the endless screw 332 illustrated in FIG. 3b. Small amounts of EPSmay also react with the conversion solution during this treatment step.The magma obtained is then passed through the filter 340 and depositedin the storage drum 360 where residual amounts of untreated EPS may alsoreact.

With reference again to FIG. 3a, the opening 311 which allows theintroduction of the EPS to be treated into the treatment vessel 310 mayalso comprise a mechanical feed system for calibrating the volume ofpolymer to be treated. This feed system is illustrated in FIGS. 5a and 5b.

FIG. 5a illustrates the main elements of the feed system which isrepresented in a general manner by reference number 400. The feed system400 is composed of a receiving vessel for the polymer 410 comprising afeed port 420 for the polymer to be treated and an outlet port 430 forthe polymer to the treatment vessel in which the process of theinvention will be carried out.

The feed port 420 comprises a first means of closure illustrated in theform of a first feed valve 422 actuated by a motor (not illustrated).The outlet port 430 comprises a second means of closure illustrated inthe form of a second feed valve 432, also actuated by a motor (notillustrated).

FIG. 5b illustrates the position of the lower part of the feed system400 on the treatment vessel 310. The second feed valve 432 is connectedto a motor 434 allowing said valve to be moved from an open verticalposition, as illustrated in FIG. 5b, to a closed horizontal position,the consequence of which would be to close the outlet port 430.

With reference once again to FIG. 5a, if it is desirable to calibratethe volume of polymer to be introduced into the treatment vessel inwhich the process of the invention will be carried out, the first feedvalve 422 is placed in an open position and the second feed valve 432 ina closed position. An amount of polymer may then be introduced into thereceiving vessel 410 until the latter is partially or completely filledwith the desired amount of polymer. The second feed valve 432 is thenplaced in an open position, the effect of which will be to cause thepolymer to be treated to fall into the appropriate treatment vessel.

It is important to note that, in the feed system illustrated in FIGS. 5aand 5 b, the presence of the first feed valve 422 is not absolutelynecessary. In fact, the polymer to be treated may be introduced into thereceiving vessel 410 with the second feed valve 432 in a closed positionwithout it being absolutely necessary, once the receiving vessel 410 isfilled in the desired manner, to close the first feed valve 422 again.

However, the first feed valve 422 may prove very useful in situationswhere a storage tank for the polymer to be treated is situatedimmediately above the receiving vessel 410. This first feed valve 422would then be essential for being able to meter the appropriate amountof polymer to be introduced into the receiving vessel 410.

FIG. 6 represents the essential steps that may be carried out for apreferred embodiment of the process of the present invention. Asillustrated by way of example, the boxes of EPS 610 undergo a waterremoval step 611 then undergo a grinding step 620. In this way, granulesare obtained which are dried 621 before being conveyed to an appropriatesilo 630. The granules are then converted in the conversion device 640either by immersion in a conversion solution or by spraying with thissolution. This conversion is followed by filtration of the impurities650 and kegging of the amorphous magma thus obtained 660.

Removal of the water consists, if necessary, in expelling the waterpresent on the EPS boxes to be treated. This removal may be carried outin a housing into which the EPS boxes are introduced. The housing may befitted with strips made of, for example, Teflon, making it possible tofacilitate the passage of the EPS boxes. Two to eight nozzles fed by ajet of air may be distributed on each side of this housing. The air maybe at ambient temperature and pressurised. The purpose of the dryingstep following the grinding step is to dry the EPS during its transportfrom the grinder to the silo. To this end, hot air is pulsed to theoutlet of the grinding stage, thus allowing the fragments of EPS to drycompletely whilst being transported. The other EPS treatment steps aresimilar to those described above.

FIG. 7 illustrates a preferred device within the context of the presentinvention. Said device comprises a system for the removal of water 711ending at the entrance to the grinder 720. The grinder outlet 720communicates with the entrance to a drier 721 connected to a storagesilo 730. The base of the silo 730 is provided with a material controlfeeder 731 connected to a conveyor 732. This latter is provided on onepart of its length with a spray system 740. The outlet of conveyor 732is connected to a filtration system 750 the outlet of which communicateswith storage drums 760.

The main advantage of this device is to allow the substantial removal ofall traces of water from the polymer before its treatment by theconversion solution.

FIG. 8 illustrates a grinding device 720 which may be used in particularin the device represented in FIG. 7. This device comprises at leastthree cylinders 822, 823, 824 arranged in a chicane, and anti-returnbars 825, 826, 827, 828. According to a particularly advantageousaspect, each of the cylinders 822, 823 and 824 which make up the grinderhas a different speed. Thus, the speed of cylinder 824 may be chosensuch as to be equal to about twice that of cylinder 822, whereas thespeed of cylinder 823 is approximately equal to three times that ofcylinder 822. The device represented in FIG. 7 having a grinderaccording to FIG. 8 makes it possible to treat more than four hundredEPS boxes per hour, these boxes having a length of 800 millimetres, awidth of 400 millimetres and a height of 300 millimetres, or more than100 m³ of EPS per hour.

The environment in which the evaporation of small amounts of solventcontained in the magma will be carried out will influence to aconsiderable extent the final structure of the product.

Generally speaking, evaporation of the solvent may be carried out inthree ways:

either by hot pulsed air at ambient pressure;

or by injection moulding under pressure; or

by curing under hot conditions with or without the application ofpressure.

a. Drying with Hot Pulsed Air

The use of hot pulsed air at the time of drying the magma according tothe invention makes it possible to produce a slightly cellular productwhich may, inter alia, be used easily as an insulating material onsmooth surfaces.

For example, the magma may be applied in the undried state to wallsurfaces. This application is followed by drying with pulsed hot airwhich produces a certain expansion of the polymer which will in thatcase constitute an effective insulation material which is easy to use.

b. Injection Moulding or Natural Drying

These two types of drying make it possible to obtain solid blocks ofresin in which the EPS is expanded very little, if at all. Drying byinjection allows more rapid solidification than natural drying.

c. Curing without Pressure

Curing the magma of the invention without the application of pressuremay also lead to expansion of the polymer.

The potential applications for the magma obtained after carrying out theprocess of the present invention are numerous and varied.

Examples of application of the paste of the present invention include,amongst others, various industrial or domestic applications which makeit possible to obtain finished articles in all forms such as piping,dishes, various boxes and protective housings.

According to another aspect of the invention, it relates to compositearticles which may be prepared from the pasty magma described above andat least one third compound. These articles may consist in pasty orliquid products such as adhesives, varnishes, coatings, sealants, paintsor lacquers and solid products consisting in particular of panels ofagglomerated particles.

An adhesive according to the invention may comprise a mixture of pastymagma with an organic solvent capable of breaking at least part of thechemical bonds between the monomers which make up the polymer. Such anorganic solvent may consist, in particular, of trichloroethylene. Anadhesive according to the invention generally contains at least 85%,preferably at least 90% by weight of pasty magma. Such an adhesive has agreater adhesive force than adhesives based on neoprene currently on themarket.

An adhesive according to the invention may also comprise 1 to 7% of acompound such as xylene. Such a compound makes it possible to obtain arelative flexibility of the adhesive film and a less abrupt rupturepoint. This adhesive may be obtained simply by mixing theseconstituents.

It is also possible to prepare a varnish or lacquers based on the pastymagma of the invention. These varnishes also comprise the basic magma,an organic solvent of the trichloroethylene type and oil of turpentine.

The adhesives and varnishes described above may also contain anti-UVagents such as phenyl-2-benzimidazole sulfenic acid.

Other composite articles according to the present invention consist insealants comprising a pasty magma as described above and plasterparticles. Such sealants contained in a sealed vessel may be stored fora long period of time, generally for more than two years. Said sealantsmay be prepared simply by mixing their components.

The invention also relates to solid composite articles prepared from apasty magma described above. These articles may be prepared simply bymechanical mixing, for example, by mixing and kneading the pasty magmaaccording to the invention with organic solid particles such asparticles of wood, natural fibres, artificial fibres, or non-organicsolid particles such as particles of metal, glass, clay powder, stonepowder or slate powder. The mixture thus obtained may then be dried andhardened.

Before drying, it is possible to add to the mixture anti-UV agents suchas phenyl-2-benzimidazole sulfenic acid. It is also possible to placethe mixture before drying in a suitable mould in order to obtain, afterdrying and hardening, an article of the desired shape. In this way, itis possible to prepare panels of agglomerated materials for varioususes. Thus, if the solid particles consist of brick particles, the panelmay be used, for example, for facade decoration. Moreover, if theparticles are wood particles, the panels may be used in the constructionof components of pallets, parquet flooring or furniture.

According to an advantageous aspect of the invention, the panels ofagglomerated particles defined above may be assembled by means of theadhesive described above. Finally, said panels may be varnished by meansof a varnish such as that mentioned above.

The solid articles according to the invention have good sealing, thermalinsulation and acoustic properties.

What is claimed is:
 1. A process for the conversion of a polymerconsisting of an expanded styrenic polymer or an expanded styreniccopolymer, characterised in that: said polymer is treated with aconversion solution comprising: a major proportion of a solvent makingit possible to modify the physical state of said polymer from anexpanded solid state to a non-expanded amorphous state such as to obtaina magma, a minor proportion of a non-greasy lubricant consisting ofglycerine or a polytetrafluoroethylene in a sufficient amount to givesaid magma a non-sticky surface state and, if necessary, a minorproportion of an alcohol in a sufficient amount to bind said solvent andsaid lubricant in said solution, said magma is recovered and, ifnecessary, all or part of said solvent is evaporated.
 2. A processaccording to claim 1, characterised in that the polymer is ground beforebeing treated with said conversion solution.
 3. A process according toclaim 1, characterised in that the polymer is immersed in the conversionsolution.
 4. A process according to claim 1, characterised in that theconversion solution is sprayed onto the polymer.
 5. A process accordingto claim 1, characterised in that the magma is filtered in order toextract the impurities therefrom.
 6. A process according to claim 1,characterised in that the solvent of said conversion solution is chosenfrom benzene, chloroform, methylene chloride, tetrachloroethylene,carbon tetrachloride, toluene or trichloroethylene.
 7. A processaccording to claim 1, characterised in that the solvent of saidconversion solution is acetone.
 8. A process according to claim 7,characterised in that the conversion solution comprises from 90% to 99%,preferably from 94% to 98% by volume of solvent.
 9. A process accordingto claim 7, characterized in that the conversion solution comprises from94% to 98% by volume of solvent.
 10. A process according to claim 1,characterised in that the non-fatty lubricant of the conversion solutionis glycerine.
 11. A process according to claim 1, characterised in thatsaid conversion solution comprises from 1% to 10%, by volume ofglycerine.
 12. A process according to claim 1, characterized in thatsaid conversion solution comprises from 1% to 3% by volume of glycerine.13. A process according to claim 1, characterised in that the alcohol ofsaid conversion solution is ethyl alcohol 95°.
 14. A process accordingto claim 13, characterised in that said conversion solution comprisesbetween 1% and 6%, by volume of ethyl alcohol 95°.
 15. A processaccording to claim 13, characterized in that said conversion solutioncomprises from 1% to 2% by volume of ethyl alcohol 95%.
 16. A processaccording to claim 1, characterized in that the polymer is expandedpolystyrene (EPS).
 17. A magma of a polymer, consisting of an expandedstyrene polymer or expanded styrene copolymer, characterised in that itmay be obtained according to the process of claim
 1. 18. A compositioncomprising: a major proportion of a solvent making it possible to modifythe physical state of an expanded polymer, consisting of an expandedstyrene polymer or expanded styrene copolymer, from an expanded solidstate to a non-expanded amorphous state in order to obtain a magma, aminor proportion of a non-greasy lubricant consisting of glycerine or apolytetrafluoroethylene in a sufficient amount to give said magma anon-sticky surface state and, if necessary, a minor proportion of analcohol in a sufficient amount to bind said solvent and said lubricantin said composition.
 19. A composition according to claim 18,characterised in that it comprises from 94% to 98% of acetone, from 1%to 10% of glycerol and from 1% to 6% by volume of ethyl alcohol 95°. 20.A solid, pasty or liquid composite article comprising a magma accordingto claim
 17. 21. A solid article according to claim 20, characterised inthat it also comprises organic solid particles such as particles ofwood, natural fibres, artificial fibres, or non-organic solid particlessuch as particles of metal, glass, clay powder, stone powder or slatepowder.
 22. A liquid or pasty article according to claim 20,characterised in that it consists of an adhesive, a varnish, a lacquer,a sealant or a paint.